Division of Atmospheric Physics within Dept of Physical Sciences, University of Helsinki is a unit (~50 persons) including meteorology and other environmental sciences. It consists of the three groups: meteorological modelling (Prof. Hannu Savijärvi), aerosol research (Prof. Markku Kulmala) and forest-air micrometeorology (Prof. Timo Vesala) and hosts the Marie Curie Chair of boundary-layer physics (Professor Sergej Zilitinkevich). These groups perform measurements of atmospheric aerosol and chemistry; and investigate their climate and health effects, surface fluxes and exchange processes between ecosystems and atmosphere including greenhouse gas budgets and carbon sinks. The theoretical resources include computer programs, e.g., for particle formation processes, air-surface fluxes, and for forest growth and CO2 exchange and cycle. The basic experimental resources consist of two field stations: SMEAR I (Lapland) and SMEAR II (Southern Finland). The Division participates in two Nordic Centres of Excellence (NCoE) and maintains close co-operation with Finnish Meteorological Institute and Finnish Institute of Marine Research, e.g., in air-sea interaction and oceanographic researches.